Hydrostatic extrusion process for producing fine gauge wires

ABSTRACT

A hydrostatic extrusion process for producing relatively fine gauge wires less than 250 Mu in diameter, wherein a liquid providing a viscosity less than 100 poise at a pressure 10,000 atmospheric is employed as the pressure medium contained in the high pressure container.

' United States Patent Hayashi et al.

1 1 Dec. 16, 1975 HYDROSTATIC EXTRUSION PROCESS FOR PRODUCING FINE GAUGE-WIRES lnventors: Makoto Hayashi; Masanori Hinata;

Minoru Yokota; Takasi Kondo, a11 of Osaka, Japan Sumitomo Electric Industries, Ltd., Osaka, Japan Filed: Feb. 6, 1975 Appl. No.: 547,853

Assignee:

Foreign Application Priority Data Feb. 6, 1974 Japan 49-15614 US. Cl. 72/60; 72/56; 72/271;

72/467 Int. Cl. B21C 23/22 Field of Search 72/56, 60, 271, 467

References Cited UNITED STATES PATENTS 10/1940 Singer 72/467 X 3,178,925 4/1965 Nolan ct a1. 72/467 X 3,344,636 10/1967 Pugh 72/271 X 3,750,264 8/1973 Nilsson 72/60 X 3,777,362 11/1973 Nilsson et a1. 1. 72/60 X 3,780,554 12/1973 3.841.129 10/1974 Nishihara 72/60 Primar E.\'aminerC. W. Lanham Assistant E.\'aminer,loseph A. Walkowski Attorney Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A hydrostatic extrusion process for producing relatively fine gauge Wires less than 250,42 in diameter, wherein a liquid providing a viscosity less than 100 poise at a pressure 10,000 atmospheric is employed as the pressure medium contained in the high pressure container.

2 Claims, 1 Drawing Figure US. Patent Dec. 16, 1975 3,926,023

HYDROSTATIC EXTRUSIVON PROCESS FOR PRODUCING FINE GAUGE WIRES BACKGROUND OF'THE INVENTION 1. Field of the Invention:

This invention relates to a hydrostatic extrusion process for producing wires, particularly extremely small gauge wires of copper, copper alloys, aluminum, aluminum alloys, gold, platinum, stainless steel and others less than 250;; in diameter.

2. Description of the Prior Art:

In the prior art hydrostatic extrusion processes which are commonly used for producing metallic wires greater than 1 mm in diameter, a high viscosity liquid such as caster oil is favorably employed for the pressure fluid in order to reduce the friction on the die face. A relatively thick fluid lubrication film of the high viscosity liquid which is formed between the die face and the outer surface of the metallic wire being extruded through the die at a high speed is on the order of several microns and is thus sufficient to reduce the friction and provide an adequate fluid lubricated condition for the hydrostatic extruded wire.

In the production of relatively fine gauge metallic wires less than 250p. in diameter, however, such prior art technique developed for relatively large diameter wires can not fiilly achieve its intended objects and the wire is still subjected to a number of problems, such as the occurance of break.

SUMMARY OF THE INVENTION It has been found by the inventors that particularly in the hydrostatic extrustion of wires with diameter less than 250p, the effect of friction resistance of the pressure liquid acting on the surface of the wire is more important than the actual unfavorable effect of friction less action on the die surface, and that the hydrodynamic lubricated condition which is considered favorable for the hydrostatic extrusion of relatively large diameter wires tends to adversely affect the surface characteristics of the wire product less than 250p. in diameter.

The primary object of the invention is to provide a hydrostatic extrusion process which is particularly adapted for the production of fine gauge wires less than 250 1. in diameter,'and wherein such fine gauge wires can be produced easily and reliably at speeds higher than 200 m/ min which is an important factor determining the commercial feasibility of the process.

It is another object of the invention to provide a hydrostatic extrusion process for producing metallic wires less than 250p. in diameter which utilizes a specific pressure fluid having a viscosity which is determined in relation to the conditions and characteristics of the hydrostatic wire stretching.

It is a still another object to provide a hydrostatic extrusion process for producing metallic Wires less than 250 1. in diameter which utilizes a specific die having an approach angle related to the condition and characteristics of the hydrostatic wire stretching.

It is a further object to provide a hydrostatic extrusion process for producing metallic wires less than 250,11. in diameter which utilizes as the pressure fluid a slow viscosity liquid exhibiting a viscosity less than 100 poise under a pressure of 10,000 atmospherics.

It is a still further object to provide a hydrostatic extrusion process wherein fine gauge metallic wires less than 250p. in diameter are extruded through a specific die having a die angle greater than 35 while using as the pressure fluid a low viscosity liquid exhibiting a viscosity less than poise under a pressure of 10,000 atmospherics.

Additional objects other than those specifically stated will become apparent on consideration of the accompanying drawing and when considered in conjunction with the specification and claims.

BRIEF EXPLANATION OF THE DRAWING:

The single FIGURE is a diagramatic view showing the relationship between the pressure of liquid used as the pressure medium for hydrostatic extrusion and the frictional resistance imparted to the wire and wherein the notation is as follows:

1 A viscosity of pressure medium wire velocity after passing through die wire velocity before passing through die extruded wire radius supply wire radius pressure of liquid 1': viscosity resistance 1: length of supply wire ho: spacing between inner wall of container 4 and supply wire 1 T: tension DETAILED DESCRIPTION OF THE INVENTION A preferred embodiment of the hydrostatic extrusion process in accordance with the invention will now be described in reference to the FIGURE.

A pressure medium 3 as well as the supply wire 1 is disposed within a pressure tight container 4 incorporating a die 2 located at the outlet end thereof through which the wire 1 is drawn and extruded outside the container 4.

The container 4 is placed in communication through a conduit 5 with a pump 6 for keeping the pressure medium 3 at the desired pressurized condition.

As the wire 1 is extruded through the die 2 at the rate V; under tension T, a force or pressure component is provided by the friction between the wire 1 and the pressure fluid 3 which acts in the opposite direction to the movement of the billet, the magnitude of such force component being represented by the following approximation:

where 1;: viscosity V wire velocity after passing through die R wire radius after passing through die R: extrusion ratio Pe: actual extrusion pressure Pi: normal extrusion pressure 1: length of moving supply wire ho: spacing between container wall and supply wire (approximately half of internal diameter of container) The pressure increase designated by (Pe Pi) in the equation (1) is caused by viscous drag of the pressure medium and thus corresponds to tension or pulling force acting on the wire away flfn the die in a usual drawing process.

The magnitude of unfavorable effect of this pressure increase becomes greater with decrease of the extruded wire diameter and, in the case of producing wires less than 250g. in diameter, it often causes a break in the wire being extruded. This problem is particularly acute in the high speed hydrostatic extrusion of such fine gauge wires which requires a wire velocity after the wire passes through the die of over 200 m/min. preferably higher than 1.000 m/min.

The use of high viscosity liquid, such as castor oil, for the primary component of the pressure medium which has heretofore been employed for smoothing the hydrostatic extrusion process for relatively large diameter wires provides no means to prevent the above problem. On the contrary. it has been found that the pressure medium in the production of particularly fine gauge wires must be selected to have a relatively low viscosity (1;) satisfying the following relation:

where Y: tensile strength of supply wire V desired wire velocity after passing through die (greater than 200 M/min) The other terms of the formula being identified in equation (1 Among many liquid mediums providing such low viscosity, kerosine, gasoline, propanol, ethanol, ethylene-glycol and buthanol are representative.

As will be understood by reading the examples hereinafter described, pressure fluid providing a viscosity less than l poise under a pressure of 10,000 atmospheres have proved satisfactory.

It has also been found by the inventors that the fluid lubrication characteristics which is effectively employed in hydrostatic extrusion processes for producing relatively large diameter wires results in a roughened wire surface which becomes increasingly appreciable as the thickness of the lubricant film increases, and does not achieve its intended effects in the case of hydrostatic extrusion process for fine gauge wires using a diamond die which effectively prevents sticking of metal.

The toughening of the wire surface by the thick fluid film lubrication characteristics may also be encountered in the high speed extrusion drawing processes which employ an extruded wire velocity on the order of l ,000 m/min and using a low viscosity pressure medium selected in the manner described above.

In order to eliminate this problem, the extrusion die should be selected to have a die semi-cone angle (a) which will prevent a fluid lubricated condition provided by the following approximate relation: 55

Y e 1 Viz/n l 81 a In other terms, the die semi-cone angle (a) of the die EXAMPLE 2 must be selected to satisfy the following relation: Samples of soft copper wire 45p, in diameter were where extruded through a die having a die angle of 45 and a: semi-cone angle of die ht: difference between half of inner diameter of die and half of final diameter of extruded wire hi: difference between half of maximum inner diameter at inlet of die and half of supply wire diameter.

The other terms in the formula being identified in formulas (l) and (A).

From the standpoint of commercial feasibility, it is desired in the extrusion of fine gauge wires to use a specific die having a die angle greater than 35 and constructed from diamond or other materials which do not readily stick to metals.

EXAMPLE 1 A 180 diameter supply wire of soft copper was drawn through a diamond die constructed to produce a finished wire product of 1. diameter under a liquid pressure of 500 kg/cm lower than the pressure at which extrusion is started without exerting any pulling force to the wire.

This procedure was repeated on a number of samples while varying the type of pressure medium and the die angle. The maximum extruded wire velocities which permitted sufficiently long-time stability in the continu- The test results of Table 1 indicate that low viscosity pressure medium such as kerosene or gasoline, etc., facilitates high speed extrusion for the production of fine gauge wires whereas when using a high viscosity pressure medium containing castor oil as the primary component which is favorably employed in the product-on of relatively large diameter wires, the extruded wire speed con not be increased sufficiently in the production of fine gauge wires.

It is noted that the viscosity of castor oil under the extrusion pressure (about 6,500 atmospheres) is 20,000 poise while the viscosity of glycerin under the same pressure is 100 poise, and kerosene and gasoline have lower viscosity than glycerin.

designed for an extruded wire product of 25p. diameter. under varying condition identical to that described in Example 1. The maximum permissible extruded wire speeds encountered in the individual tests are shown in Table 2. The test results of Table 2 demonstrate the favorable effect of using a low viscosity oil as the pressure medium still more clearly than do the test results of Table 1. In order to achieve a commercially feasible extrusion rate v higher than 200 m/min, it has been found necessary to use a low viscosity pressure medium such as kerosene or gasoline, etc.

TABLE 2 Pressure Medium Maximum Extruded Wire Speed Glycerin-Ethylene Glycol First Grade kerosene Gasoline EXAMPLE 3 A supply wire of soft copper of 80p. diameter was extruded through a die having a die angle of 60 and designed to produce an extruded wire of 40p. diameter while using a pressure medium consisting of glycerin and ethylene glycol mixed in the ratio of 4 l. The temperature of the pressure medium was increased while the pressure thereof was maintained at l0,000 Kg/cm The maximum permissible extruded wire speeds determined at different temperatures are shown in Table 3. The test results confirm that a reduction in the viscosity of the pressure medium contributes to considerable increase in permissible extruded wire speed.

TABLE 3 Temperature of Maximum Permissible Viscosity of Pressure Medium Extruded Wire Speed Grycerin 25C Less than 400 m/min 500 poise 70C Up to 2,000 m/min, poise assuring stable extrusion operation EXAMPLE 4 TABLE 4 Extruded Wire Speed (m/min) Die Angle While in the above examples kerosene, gasoline monomer and glycerin-ethylene glycol heated up to C were employed by themselves as the pressure medium, these liquids may be used as a mixture thereof and may be heated sufficiently to provide a viscosity less than poise at a pressure of 10,000 atmospheres. Further, a fatty acid, an extreme-pressure additive and the like may be added to the pressure medium to improve the wettability and lubrication property.

It should also be noted that the method of the present invention is applicable to wire production with any kind of metal, not just copper. For example, fine gauge wires of aluminum, gold, stainless steel and others can readily be produced in accordance with the method of the invention.

From the foregoing, it will be appreciated that the invention provides an improved hydrostatic extrusion method which employs a specific pressure medium providing a limited viscosity and a specific die having a limited die approach angle, and wherein relatively small gauge metal wires less than 250p. in diameter can be produced with improved product quality and substantially cheaply as compared to the prior art extrusion drawing process.

What is claimed is:

1. ln a hydrostatic extrusion process for producing relatively fine gauge wires less than 250a in diameter by liquid pressure extruding a metal ingot of larger diameter than that of a die opening, through said die opening of a high pressure container, the improvement wherein a liquid providing a viscosity less than lOO poise at a pressure of l0,000 atmospheric is employed as the pressure medium contained in the high pressure container.

2. In a hydrostatic extrusion process for producing relatively fine gauge wires less than 250p. in diameter, by liquid pressure extruding of a metal ingot of larger diameter than that of a die opening, through said die opening of a high pressure container, the improvement wherein a liquid providing a viscosity less than 100 poise at a pressure of 10,000 atmospherics is employed as the pressure medium contained in the high pressure container and the wire is extruded through said die which has a die approach angle greater than 35. 

1. In a hydrostatic extrusion process for producing relatively fine gauge wires less than 250 Mu in diameter by liquid pressure extruding a metal ingot of larger diameter than that of a die opening, through said die opening of a high pressure container, the improvement wherein a liquid providing a viscosity less than 100 poise at a pressure of 10,000 atmospheric is employed as the pressure medium contained in the high pressure container.
 2. In a hydrostatic extrusion process for producing relatively fine gauge wires less than 250 Mu in diameter, by liquid pressure extruding of a metal ingot of larger diameter than that of a die opening, through said die opening of a high pressure container, the improvement wherein a liquid providing a viscosity less than 100 poise at a pressure of 10,000 atmospherics is employed as the pressure medium contained in the high pressure container and the wire is extruded through said die which has a die approach angle greater than 35*. 